Physical And Chemical Characterization Of Carbon Nanotubes In Aqueous Solution And Blood Compatibility

It is the particular structural of carbon nanotubes (CNTs) that determine their application prospects in the biomedical field. Carbon nanotubes have been investigated as novel delivery systems for drugs, DNA/RNAs, proteins, as imaging contrast agents and detection devices for capturing tumor cells. Well characterization of carbon nanotube dispersing in the aqueous solution is crucial for their biomedical applications; however, most of the conventional tools and instruments are only suitable to the nanomaterials in solid state.Understanding blood compatibility of carbon nanotubes is important for designing their biomedical applications. It have been reported that carbon nanotubes can cause platelet activation and aggregation; and a certain concentration of carbon nanotubes can inhibit the viability of vascular endothelial cells. However, the details of interactions between carbon nanotubes and blood still remain largely unexplored; in particular, the influences of carbon nanotubes on red blood cells and thrombus mechanical properties have been rarely reported.In this work, we conducted following researches:(1) Prepare multiwalled carbon nanotubes in carboxylization or amimation by concentrated acid and ultrasonic oxidization technologies. By controlling ultrasonication time to prepare oxidized multiwalled carbon nanotubes with different oxidation degree, and by carbodiimide catalysic reaction to prepare carbon nanotubes with amino group.(2) Establish physicochemical characterization system for multiwalled carbon nanotubes dispersing in the aqueous solution on the basis of UV-vis-NIR spectroscopy, in combination with other analysis methods including scanning electron microscopy (SEM), dynamic light scattering (DLS), Fourier transform infrared spectrometer (FTIR), thermogravimetric (TGA) and X-ray photoelectron spectroscopy (XPS).(3) Investigate the interactions of carbon nanotubes to the components of blood using environmental scanning electron microscope (ESEM), flow cytometry, recalcification, thromboelastography (TEG) and TEM. Investigate the effects of multiwalled carbon nanotubes with diferent length and different surface chemistry on the activity of vascular endothelial cells (Ea.hy926) cell.The scientific findings include following points: (1) Oxygen-containing groups including carboxyl acid group were introduced to the MWCNTs. With the ultrasonic time increased, relative amount of carboxyl acid group was elevated. By reacton between carboxylic group and amino group, the carboxylized multiwalled carbon nanoutbes could be aminized.(2) The characterized UV absorption spectrum for the multiwalled carbon nanotubes were resolved into three peaks. It was found that the area and position of the resolved peaks were related to the size distribution and the oxidation degree of CNTs respectively. The peak position of the main peak gradually increased with increasing nanotube length. With the increase of the degree of carbon nanotube oxidation, peak intensity of the main peak gradually increased.(3) When the multiwalled carbon nanotubes dispersing in the aqueous solution aggregated and leave off the water phase, the main peak occurred red shift. After centrifugation with different speed, the peak intensity for the multiwalled carbon nanotube decreased, but the peak position did not change significantly. Hence the dispersion stability of multiwalled carbon nanotubes can be characterized using UV-vis-NIR spectroscopy under either static or centrifugation.(4) The MWCNTs with long or short length and carboxylic or amino group induced red blood cell damage with different degrees. The multiwalled carbon nanotubes also caused a mild level of platelet activation (10-25%). L-COOH and L-NH2induced a higher level of platelet activation than S-COOH and S-NH2respectively; meanwhile L-NH2caused marked reductions in platelet viability. The presence of the four MWCNTs, particularly L-COOH led to earlier fibrin formation and softer clots. It was concluded that the four MWCNTs affected blood coagulation process and the clots mechanical properties; they also altered the integrity of the red blood cells and the viability of the platelets, as well as induced platelets activation. The effects of MWCNTs depended on the size and chemistry of the nanotubes and the type of cells they contacted.